React Native Facebook SDK Initialization on Android

I am integrating the Faecbook SDK into an existing react-native project and having the dreaded error: The SDK has not been initialized, make sure to call FacebookSdk.sdkInitialize() first.

I have followed the instructions carefully, so strings.xml contains:

<string name="facebook_app_id">xxxxx</string>

And in AndroidManifest.xml, inside the application element, I have

<meta-data android:name="com.facebook.sdk.ApplicationId" android:value="@string/facebook_app_id"/>

I've made the changes to settings.gradle and build.xml as described.

All the instructions say that I shouldn't need to call FacebookSdk.sdkInitialize() if I have done the above. I'm using react-native-fbsdk version 1.1.1 and react native 0.60.5

When I followed the instructions on a simple new react-native project it works, so I am wondering if it is a conflict with something in the app, but I'm not sure what to look for. Can anyone suggest how to debug?

Thanks.